Did the Emperor avoid developing the Primarchs' powers?

Question

We know that the Primarchs were probably all or mostly psykers of some degree. We also know, however, that most of them didn't exhibit significant powers compared to most major canon psykers. Nor do most of them seem to have received training for these inherent powers, which seems odd if they're intended to be the best possible soldiers.

Given that psychic powers are heavily tied to the Warp and thus even the Chaos Gods, one might imagine that the Emperor would see being a powerful psyker as a risk, despite himself fitting that description. Is there any evidence in the books or codices that the Emperor intentionally avoided helping his children reach their full potential?

Answer 1

There is no official source saying so however we can speculate.

While the Emperor never really shared much about his true goals we do know one thing, he wanted to destroy the chaos gods but he first seemingly needed to conquer most of the milky-way galaxy in order to do so.

It is my personal belief that some(maybe all) the primarchs were created in some extend to fight the chaos gods, Lion el Johnson for example could ignite his weapons with white psychic fire when he fought the deamons that invaded his ship the invincible reason. It is also heavily hinted that all primarchs are themselves a fusion between warp and reality, for when Corvus Corax entered the warp he could transform himself into a flock of ravens. Coupling with the fact that every primarch seemingly is the equal or greater than the greater deamons of chaos they paint a eerily comparison that they themselves are greater deamons of the Emperor of some sort.

This is pure speculation on my part but i believe the Emperor wanted to first take over the galaxy and then tell his sons about chaos and how they were going to fight it. But as we all know he never got the chance to do so because someone screwed everything up.

So in conclusion i think he avoided preparing his sons to fight the warp until he himself was ready to take the fight to the chaos gods.(which ultimately allowed their corruption because they did not even know the warp housed sentient beings )

Answer 2

There is evidence of the opposite, Magnus was taught by the Emperor about his psychic powers even before the 2 of them met. The Emperor gave him enough to be safe (as he thought) and then left him to it telling him to take it slow and be careful.

We know how that ended, Magnus went off and ended up bargaining away his soul.

The Emperors approach generally with knowledge of the warp was to give just enough to warn against the powers without explaining why. Remember his ultimate goal was to breed the psychic gene out of all of humanity and then let the forces of chaos die of starvation. Magnus was raised to sit on the golden throne and control the entrance into and navigation through the webway, this would then allow the navigators to be disposed of and humanities reliance on the warp would end. So he allowed enough to be taught to allow psychic powers to be used as a weapon without actually teaching the truth of where is came from.

The Emperor was genuinely surprised that his sons turned against him and in the buried dagger book he tells the Knights Errant that this sons turned to and used the forces of Chaos against him without understanding what they did so even at this point he does not realise that the forces of Chaos where behind everything.